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And I talk about scenario where you explicit let users know MITM is happening and where users must comply (for example, Kazakhstan wanted to have a national-wide MITM proxy, to protect their citizens from malicious foreign websites, even go as far to ask Mozilla to include their CA.)

But I just can't think of a scenario where you don't have to manage the connections between the MITM proxy and Remote server. And that feels very expensive to me to do on a national scale.

Thus my question:

Is it possible to MITM TLS without maintaining connection between proxy and remote server? When the client will comply with your order to install Root CA certificate.

Let's assume we need to handle HSTS as well, and users are using normal browsers.

(Of course, using backdoors on OS/Browser will be easier than hijacking TLS, but let's assume we have to go the hijack route.)

  • Side note: maybe there are ways to maintain such connections efficiently so that performance is not an issue even on national scale, if so, I am interested to read any existing solutions... – bitinn Jan 24 '17 at 6:56
  • You mean TCP connections? – Silver Jan 24 '17 at 6:56
  • @Silver standard way of MITM proxy requires opening a connection from proxy server to remote server using normal TLS flow. I am asking if that can be avoided or reduced. – bitinn Jan 24 '17 at 7:04
  • For what it's worth, expensive or not Kazakhstan just did implement nation wide MITM as they tried/threatened to do a few years back. – Caleb Jul 19 at 8:11
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I just can't think of a scenario where you don't have to manage the connections between the MITM proxy and Remote server. And that feels very expensive to me to do on a national scale.

Not particularly. Primarily this is because you don't do it at a national scale - you require ISPs to do it for you, and you just hook into them to do your offline data processing (a la Room 641A, if you're doing passive surveillance).

Besides, the traffic isn't really that much for a fairly simple TLS termination. Kazakhstan only has around 18 million people, and 13.2 million internet users; Stack Overflow has about half that, plus they have to run a whole website for them. TLS is pretty cheap now, and governments can usually get funding pretty easily for "national security", "defense against terrorists", and things like that.

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Is it possible to MITM TLS without maintaining connection between proxy and remote server?

From a technical point this is impossible. TLS MITM is only possible by having separate TLS connections from the proxy to both the client and the server. You need to maintain the state of both the TCP and the TLS stack for the full duration of the interception because otherwise you could not receive, decrypt, re-encrypt and send the data from the client to the server and back. But this does not need to be done on a single machine but can be made to scale will over thousands of systems.

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